In Khaziel there is a challenge called The Grudge which has a Fortress Gate as the first troop. There is another one with this set up in Broken Spire with FG in first position called Fortress Seige. The benefit with these setups is with the gate in first position with 0 attack you don’t have to worry about skulls being fired off at you. The only concern is you have to try not to fire skulls yourself and take out the wall. Just remember doing these repeats only gives the traitstones offered from each of the kingdoms (Khaziel - Earth and Arcane Deep / Broken Spire - Earth and Water and Arcane Shield).
My soul farming team is Valkyrie - Alchemist - Sunweaver - Griffon Knight. With Celestial armor and on normal difficulty I fire Val off 4 times and get the max of souls. But if you don’t have some of those the team I started with was Hero with Crude club - Deep Borer - Valkyrie - Alchemist. DB feeds Alchemist which feeds Valk which feeds DB.
I hope this is more helpful. I’ve pretty much given up on traitstone farming myself. I buy them in the glory packs.